The present invention relates to a method of manufacturing a semiconductor device having a capacitor using a high permittivity dielectric film or a ferroelectric film as a capacitor dielectric film, and in particular, to a method including a step of dry etching of the capacitor dielectric film.
Recently, efforts are concentrated on development of a microcomputer incorporating a capacitor using a high permittivity dielectric film or a ferroelectric film, being effective as measures for decreasing extraneous emission which is an electromagnetic noise, and a ferroelectric nonvolatile RAM capable of operating at low voltage and writing/reading at high speed. Etching of these capacitor dielectric films has been done by wet etching as isotropic etching or non-selective ion milling. In these methods, however, high processing accuracy and high etching selectivity cannot be realized, and hence dry-etching technique is lately researched and developed intensively. The etching gas used in dry-etching of capacitor dielectric films and electrodes is halogen represented by chlorine or its compound. For example, chlorine alone, hydrogen chloride and carbon chloride have been reported.
A conventional method of manufacturing a semiconductor device is described below by referring to drawings. FIG. 4(a), FIG. 4(b), FIG. 4(c), and FIG. 4(d) are sectional views for explaining the method of forming a capacitor included in a conventional semiconductor device.
First, as shown in FIG. 4(a), a platinum bottom electrode film 1, a dielectric film 2 comprised of a high permittivity dielectric film or a ferroelectric film, and a platinum top electrode film 3 are formed on a substrate 4 on which a silicon oxide film is deposited. Then, using a photoresist film 5 as mask, the platinum top electrode film 3 and the dielectric film 2 are dry-etched by using etching gas containing chlorine and processed into a shape as shown in FIG. 4(b). Finally, by dry-etching the platinum bottom electrode film 1, a capacitor is formed.
In this conventional manufacturing method, however, a defect 8 be formed in a side wall 6 of the dielectric film 2 as shown in FIG. 4(c) or the side wall 6 is often degenerated into a difference substance 9 from the dielectric. When such state appears, short circuit of capacitor or increase of leakage current occurs, and the function as the capacitor is lost in an extreme case.
The cause of appearance of such phenomenon may be considered as follows. On the side walls 6 of the platinum top electrode film 3 and the dielectric film 2 which are dry-etched, and on the surface 7 of the platinum bottom electrode film 1 which is exposed, atoms, ions or radicals of chlorine generated by decomposition of the etching gas due to discharge are massively deposited. These chlorine atoms, ions or radicals easily react with moisture to form an acidic aqueous solution, that is, hydrochloric acid. The side wall 6 of the dielectric film 2 composed of a dielectric oxide violently reacts with this hydrochloric acid, and the dielectric film 2 is eroded, or degenerated into other substance 9 different from the dielectric. As a result, it is considered to lead to short circuit of capacitor, increase of leakage current, or loss of function as capacitor.
This adsorption of moisture occurs always in operation in the manufacturing process of a semiconductor device such as exposure of substrate to the atmosphere or washing in water, and is hence inevitable. Such inconvenience is also noted when using bromine or iodine as etching gas.